A circulating valve is generally used during different well operations in subterranean oil and/or gas wells. The circulating valve is lowered into the well bore by means of a tubular string. In its open state, circulating valves allow fluid to flow from the inside of the string to the well (or in the reverse direction). The circulating valve may be brought from its open state to a closed state wherein no fluid flow is allowed. The control of the circulating valve is performed from the topside, either by applying one predetermined pressure, applying several pressure pulses, or by increasing the fluid flow over fixed exit ports.
U.S. Pat. No. 4,403,659 describes a pressure controlled reversing valve comprising a housing with fluid ports being closed by means of a valve sleeve mounted on a spring-loaded mandrel. Two J-slot channel arrangements are used to control the opening/closing cycle of the valve. This reversing valve is closed in its initial state.
U.S. Pat. No. 6,104,345 describes a circulating valve which is responsive to the fluid flow rate through the valve. The valve comprises a housing and a mandrel provided inside the housing. The mandrel comprises a radial flow port, a biasing member, a ratchet with a J-slot channel arrangement, an inner sleeve and a one-way flow restrictor carried on the mandrel.
There are several disadvantages With the above valves. First of all, they are relatively complex, and they are also vulnerable to operation failure. The above valve use ports with relatively small diameter to achieve pressure differences. Hence, the valves are vulnerable to debris obstructing the ports. Moreover, these valves use only a small portion of the flow in order to control the operation of the valve, since most of the fluid is flowing through the through bore.
The object of the invention is to provide a reliable and relatively simple circulating valve. It is an object to provide a valve which is actuated by changing the fluid rate through the valve. Moreover, it is an object of the invention to be able to pressure test the inside of the string above the valve and the well below or outside the wall before re-opening the valve after a closure.
It is also an object of the invention to provide a valve which easily can be adapted to different wells, i.e. with respect to different well pressures, well fluids etc.
The circulating valve may replace ball subs, where it saves a significant amount of time waiting for activating halls to land. It also reduces risk in deviated wells where balls may have difficulties landing due to a combination of restrictions and gravitational effects. The circulating valve may also be used for flow control underneath bridge plus, packers, etc or for pressure testing of completion packers after installation.
Moreover, the circulating valve may be used in situations where a temporary barrier and circulation possibility are needed to avoid wireline intervention during completion or recompletion of the well.